The invention relates to a medical instrument with a distal end area on which jaw parts are arranged which are movable relative to one another and pivotable about an axle pin, said axle pin being received in an opening of the medical instrument.
Medical instruments of this kind, for example dissecting forceps, grasping forceps, and scissors, are marketed by the Applicant.
Various versions of these medical instruments are described in the catalog “Laparoskopie” [Laparoscopy] from the same company (5th edition January 2004, section 4 entitled “Präparier-und Fasszangen” [Dissecting forceps and grasping forceps] and section 5 entitled “Scheren, Stanzen, Zangen für Probeexcision” [Scissors, punches and forceps for excision of samples]).
The abovementioned medical instruments are used in the field of minimally invasive surgery.
In laparoscopy and thoracoscopy, the minimally invasive versions of operations on the gallbladder, cecum and esophagogastric junction, in treatment of reflux disease and inguinal hernia, and in surgery of the joints and spinal column, have proven best.
In all these techniques, the operations are performed through relatively small openings. The surgeon's view is in this case afforded by use of endoscopes, which can be connected to a video chain and thus permit telesurgery. The extremely small accesses with incisions of 5 to 10 millimeters demand the use of slender instruments.
The medical instruments used in minimally invasive surgery have a structure made up of several parts.
Medical scissors for minimally invasive surgery usually comprise a shaft measuring approximately 30 to 50 cm in length. Arranged at the proximal end of this shaft there is a scissor-like handle which is connected to the jaw parts, arranged at the distal end, by way of a rod-shaped actuating element displaceable in the interior of the shaft.
At the distal end area, a toggle mechanism, for example, is connected to the rod-shaped actuating element. This toggle mechanism transmits the pushing and pulling forces to jaw parts, which are movable relative to one another, or, more precisely, are mounted pivotably about an axle pin extending transversely with respect to the longitudinal axis of the shaft. Designs in the form of grasping, gripping or cutting instruments are known, including those for electrocoagulation.
Since the instruments in minimally invasive surgery are inserted into the body through trocars, the clear internal diameter of the trocar sleeve engaged in the body determines the size of the components of the medical instruments, for example the length of the transversely extending axle pin.
Moreover, the medical instruments should be reusable. During their use, smaller components in particular often have to be able to cope with considerable stresses.
The forces which can arise during dissection, cutting and resection, for example if the operating surgeon strikes the instrument against bone, have to be taken up in an optimal manner by the axle pin and carried to the medical instrument. The same applies to pressing and pulling forces which are applied to the axle pin by the scissor-like handle via the rod-shaped actuating element.
The small dimensions of the axle pin, of only about 5 mm length and about 1 mm diameter, therefore mean that a particular structure is desirable for taking up and transmitting forces.
The medical instruments should also have no niches in which bacteria can gather. They must be easy to dismantle for mechanical or manual cleaning and, in addition, must be able to be completely sterilized in modern autoclaving procedures.
In the course of cleaning and sterilizing of the medical instruments, smaller components are once again exposed to considerable stresses. During the mechanical or manual cleaning of the instruments, mechanical influences may arise, such as impacts or pressure loads and tensile loads. Moreover, in standard protocols used today in modern flash autoclaving, the individual components have to withstand temperature jumps and high temperatures of up to 165° C. with saturated live steam. Resistance to various forms of corrosion is therefore a prerequisite.
Fragmenting, for example, of parts or all of the axle pin must be avoided under all circumstances, both for reasons concerning reliability for the user and also concerning the safety of the patient being treated, since fragments remaining in the patient's body can cause health problems.
The known medical instruments employed usually have a rivet with a circular head as their axle pin.
In practice, it has now been found that the axle pin with a circular head may come loose during the use of the medical instrument and turn about its own axis. This turning about its own axis intensifies during further use, such that the axle pin becomes worn and widens its path. Dirt traps thus form which can be accessed only with difficulty for cleaning. In addition, optimal handling of the medical instrument is no longer possible. Necessary repairs then in most cases entail complete replacement of damaged components. Lateral slipping not only leads to unreliability of function but also possibly to the jaw parts falling off, which would cause serious problems during an operation.
It is therefore an object of the present invention to remedy this situation and to develop a medical instrument of the stated type in such a way that it has an axle pin whose function is reliably maintained on a permanent basis.